public with sharing class SetUsage {
public void setUse(){
Set<Integer> st = new Set<Integer>();
st.add(1234);
st.add(1248);
st.add(1225);
st.add(1252);
System.debug('----------------Elementa in the set are --------------'+st);
System.debug('----------------Size of Elementa in the set are ------4--------'+st.size());
st.remove(1252);
System.debug('----------------Size of Elementa after removing an element in the set are ------3--------'+st.size());
st.add(1248);
st.add(1252);
st.add(1221);
System.debug('----------------Size of Elementa in the set after adding duplciates are ------5--------'+st.size());
Set<Integer> newst = st.clone();
System.debug('----------------Size of Elementa in the new set are -------5-------'+newst.size());
st.clear();
System.debug('-----------------NEw set is EMpty or not--------false--------'+newst.isEmpty());
for(Integer i: newst){
System.debug('----------------->'+i);
}
}
}

- As per the above screen shot set the OWD value for isBypassed as 'False'
- Add two users by clicking on New button, set isBypassed as 'True' for one user and 'False' for another user

3. Create a page called 'Change Owner'

<apex:page tabStyle="Case" standardController="Case">
<apex:form >
<apex:sectionHeader title="Change Case Owner"/>
<p>This screen allows you to transfer cases from one user or queue to another. When you transfer ownership, the new owner will own:</p>
<ul><li>all open activities (tasks and events) for this case that are assigned to the current owner</li></ul>
<p>Note that completed activities will not be transferred. Open activities will not be transferred when assigning this case to a queue.</p>
<apex:pageBlock mode="Edit">
<apex:pageBlockButtons location="bottom">
<apex:commandButton value="Save" action="{!save}"/>
<apex:commandButton value="Cancel"/>
</apex:pageBlockButtons>
<br/><apex:pageBlockSection title="Select New Owner" collapsible="false" columns="3">
<apex:pageBlockSectionItem >
<apex:outputLabel value="Owner"></apex:outputLabel>
<apex:inputField value="{!Case.ownerId}"/>
</apex:pageBlockSectionItem>
</apex:pageBlockSection>
</apex:pageBlock>
</apex:form>
</apex:page>

- Use the above script for OnClick JavaScript
- Add the above custom button 'Change Owner' to Case Page Layout.
- "{!$Setup.Disable_Change_Owner__c.isBypassed__c}" is the way to refer the hierarchy custom setting in JavaScript.
- According to the above button one user can access the page and navigate to the 'Case Owner' page

- Another user is not able to access the page, it will throw JavaScript alert